Doctors have been checking the pupil light reflex (PLR) and size of the pupils of patients with suspected brain injuries or impaired consciousness for more than 100 years. Traditionally, these measurements have been performed in a very subjective and qualitative fashion. Doctors have used pen flashlights to test the reactivity of patients’ eyes, and a pupil gauge to measure their size.
Engineers at NeurOptics (Irvine, CA, USA) have developed a handheld infrared device that automates the entire procedure, providing more reliable and objective measurements.
The NeurOptics device -- called a Pupillometer -- captures IR images of the pupil 30 times per second over a 2-s period, after which it provides the average pupil diameter and standard deviation with an accuracy that is greater than 0.1 mm. The measurement results are then displayed on the device's color LCD screen.
When doctors score the reaction of pupils as part of the neurological evaluation of a patient, pupils are classified as brisk (or normal), sluggish, or nonreactive, all of which are subjective terms.
To perform the same function automatically and more objectively, a neurological pupil index (NPi) algorithm in the Pupillometer provides a numerical NPi value between zero and five. An NPi value equal to or greater than three is considered a normal pupillary reaction as defined by the algorithm, and an NPi value below three is considered an abnormal pupillary reaction.
Thanks to the new unit, even the smallest changes in the function of the pupils -- even those that are not discernable to the naked eye -- are now detectable by clinicians and can be measured and quantified.
-- Posted by Vision Systems Design
